In general, as a typical large-scale display device, a Liquid Crystal Display (LCD), a Plasma Display Panel (PDP), etc. is used.
Unlike the self-emission type PDP, the LCD requires a separate backlight unit due to absence of a self light emitting element.
A backlight unit for use in the LCD is classified into an edge type backlight unit and a direct type backlight unit according to a position of a light source. In the edge type backlight unit, light sources are disposed at left and right side faces or upper and lower side faces of an LCD panel and a light guide plate is provided to uniformly disperse light throughout a front surface of the LCD panel, thereby ensuring uniform luminance and enabling production of an extremely thin display panel.
The direct type backlight unit is generally applied to displays of 20 inches or more. The direct type backlight unit advantageously has greater lighting efficiency than the edge type backlight unit owing to a plurality of light sources being disposed beneath a panel, and thus is mainly used in large-scale displays requiring high luminance.
The conventional edge type or direct type backlight unit adopts a Cold Cathode Fluorescent Lamp (CCFL) as a light source.
The backlight unit using the CCFL, however, has several disadvantages, such as consumption of a great quantity of power because power should always be applied to the CCFL, low color reproduction efficiency of about 70% that of a Cathode Ray Tube (CRT), and environmental pollution due to use of mercury.
Currently, a backlight unit using a Light Emitting Diode (LED) is being studied as a solution to the above-mentioned problems.
In the case of the backlight unit using the LED, turning on or off a part of an LED array is possible, which can achieve remarkable reduction in power consumption. In particular, an RGB LED exhibits color reproduction beyond 100% of a color reproduction range proposed by the National Television System Committee (NTSC) and can provide more vivid images to consumers.
Further, the LED, fabricated through semiconductor processes, is environmentally friendly.
Although LCD products using the LED having the above-mentioned advantages have been introduced, these LCD products require expensive drivers, PCBs, etc. because the LED has a driving mechanism different from the conventional CCFL. For this reason, the LED backlight unit is applied only to high priced LCD products at present.
In the case of the LED backlight unit for guiding light through air without use of a separate light guide plate for guiding light emitted from the LED array to the front of a display device, a structure of a bottom cover is important in order for light emitted from the LED array to be reflected and guided to the front of the display device.